exhaust

[hifi875]

i had 40series flows on my camaro for years, got tired of the interior drone, so i bought 40series delta flows, was told they would help out tremendously by flowmaster themselves. put them on and it sounds the exact same inside! called them and they said i have too much motor (413 sbc). i have 2.5 exhaust w/dr.gas xpipe ran out the back. any suggestions on amuffler system that will give me good exterior sound w/minimal interior resonance? thanks